Degradable polyurethane resin

ABSTRACT

The invention is a degradable polyurethane resin obtained by reacting 2,5-/2,6-diisocyanatomethylbicyclo[2.2.1]heptane and/or a modified compound thereof with polyol comprising a single compound, mixture or copolycondensate selected from the group consisting of (A) polyhydroxycarboxylate polyol, (B) aliphatic polyester polyol and (C) saccharides, or (D) straight or branched polyol formed by condensation of (A) and/or (B) with aliphatic polyhydric alcohol having functionality of three or more, and the polyurethane resin has hydralyzability and biodegradability, is excellent in rigidity and elasticity in combination with flexibility as compared with conventionally known biodegradable resin, and can provide formed articles having outstandingly high elasticity and elongation and other unprecedented properties.

TECHNICAL FIELD

The present invention relates to a novel polyurethane resin of specificstructure obtained by using2,5-/2,6-diisocyanatomethylbicyclo[2.2.1]heptane and/or a modificationproduct thereof as a bonding agent, and more specifically relates to anovel polyurethane resin having decomposing ability, that is,hydrolyzability and biodegradability and a molded article prepared fromthe same.

TECHNICAL BACKGROUND

In recent years, environmental pollution due to plastic waste has becomea global problem. The greatest cause of the problem lies in the factthat plastics such as polystyrene, polyvinyl chloride, and polypropylenewhich constitute most of the waste have no biodegradability and thusremain as intact in the soil even after land fill disposal.

When incinerated, plastics have generally large combustion heat andcombustion gas causes environmental pollution. Thus, it is difficult toconform to the problem by usual incineration equipment alone. Althoughrecycle has gradually become widespread, a considerably large portion ofplastics application area is essentially inadequate for recycle.

On such present situations, development of biodegradable plastic whichcan decompose under natural environment, has been carried out. Manybiodegradable resins have already been known. Representative resins arepolyglycolic acid, polylactic acid, polyhydroxybutyric acid,polyhydroxyvaleric acid, polycaprolactone and otherpolyhydroxycarboxylic acids; and polybutylene succinate, polybutyleneadipate and other aliphatic polyesters which can be obtained bypolycondensation of polyhydric alcohols and polybasic acids. Othermaterials which are investigated for application are polysuccinimide andother polyamino acids; molasses, cellulose, modified cellulose, chitin,chitosan and other saccharides and modified materials thereof; resinsderived from gelatin, sericin, lignin and other modified proteins; andnatural high polymers from vegetable oils.

However, in order to substitute the above biodegradable resins forconventionally used resins in many application fields, physical,mechanical or chemical properties are still unsatisfactory.Particularly, polylactic acid is the sole colorless and transparentplastic in the biodegradable resins and is excellent in the tensilestrength. On the other hand, polylactic acid has low elasticity andelongation and is disadvantageous in brittleness. Further, many of theseplastics have difficulty in preparation and thus many improvements havebeen carried out.

One of these improvements is a process for reacting an aliphaticpolyester oligomer with a polyisocyanate compound. For example, aprocess for preparing aliphatic polyester by reacting polylactide withpolyisocyanate has been disclosed in Japanese Laid-Open Patent HEI5-148352. Examples for using a polyisocyanate compound as a bondingagent of polyhydric alcohol and polybasic acid in the preparation ofaliphatic polyester have been described in Japanese Laid-Open Patent HEI4-189822 and 6-157703. Examples for bonding saccharides withpolyisocyanate have been disclosed in Japanese Laid Open-Patent HEI9-302061. However, the polyisocyanate compounds used in these patentsgenerally have high toxicity and diamine which develops by decompositionof isocyanate is also hazardous to natural environments. Consequently,hexamethylene diisocyanate or isophorone diisocyanate which is not sohazardous to natural environments has been used in Japanese Laid OpenPatent HEI 5-70543 and 5-50575. However, hexamethylene diisocyanateleads to operation difficulty due to high vapor pressure in preparingbiodegradable resins, and the resulting resin is disadvantageous in lowbreaking strength and breaking strength, though excellent in elongation.

On the other hand, isophorone diisocyanate differs in the activity ofthe two isocyanate groups and has a very low reaction velocity whichcauses problems on preparing the biodegradable resin.

The subject of the present invention is to provide, in view of theproblems in the conventional technology, a novel degradable resin havingimproved properties as compared with conventional biodegradable resin.Another subject of the invention is to provide a resin and a moldedproduct thereof which can be safely abandoned in the natural environmentas compared with conventional technology, can be obtained under mildreaction conditions and have decomposability, that is, hydrolyzabilityand biodegradability.

DISCLOSURE OF THE INVENTION

As a result of an intensive investigation in order to achieve the abovesubjects, the present inventors have found that a polyurethane resinobtained by using 2,5-/2,6-diisocyanatomethylbicyclo[2.2.1]heptane(hereinafter referred to simply as NBDI) which is no mutagenicity incorresponding amine as a bonding agent of the degradable resin cansurprisingly enhance elongation and elasticity while maintaining orimproving the strength of the known biodegradable resin and that abiodegradable polyurethane resin can be prepared under mild conditions.Thus, the present invention has been completed.

That is, the aspects of the invention can be illustrated by thefollowing items.

(1) A degradable polyurethane resin characterized by resulting fromreaction of polyol with 2,5-/2,6-diisocyanatomethylbicyclo[2.2.1]heptanerepresented by the formula (1);

wherein the two isocyanatomethyl groups are located on 2,5-positions or2,6-positions or a mixture thereof, and/or a modified compound thereof,wherein the polyol is a single compound or a mixture or acopolycondensate of one or more compounds selected from the groupconsisting of (A) polyhydroxycarboxylate polyol, (B). aliphaticpolyester polyol and (C) saccharides, or (D) straight or branched polyolresulting from condensation of (A) and/or (B) with aliphatic polyhydricalcohol having functionality of three or more,

(2) A degradable polyurethane resin according to the above item (1)wherein the polyhydroxycarboxylate polyol is obtained by modification ofthe terminal carboxyl group to a hydroxyl group in the aliphaticpolyhydroxycarboxylic acid represented by the formula (2);

wherein R¹ is an alkylene group having 1 to 4 carbon atoms in thestraight chain portion and having 1 to 6 total carbon atoms whichinclude branched alkyl groups, and m is an integer of 1 or more.

(3) A degradable polyurethane resin according to the above item (2)wherein R¹ in the formula (2) is an alkylene having 1 carbon atom,alkylene having 1 carbon atom in the straight chain portion andsubstituted by methyl, ethyl or propyl, or having 2 carbon atoms in thestraight chain portion and substituted by methyl or ethyl, or having 3carbon atoms in the straight chain portion and substituted by methyl,and R¹ in the formula (2) is aliphatic polyhydroxycarboxylate polyolcomprising the same or different structural units,

(4) A degradable polyurethane resin according to the above item (1)wherein aliphatic polyester polyol is obtained by reacting a singlecompound or mixture selected from aliphatic polyhydric alcoholrepresented by the formula (3);

HO—R²—OH  (3)

wherein R² is an unsubstituted or substituted aliphatic hydrocarbongroup having 2 to 20 carbon atoms, with a single compound or mixtureselected from aliphatic polybasic acid represented by the formula (4);

HOOC—R³—COOH  (4)

wherein R³ is an unsubstituted or substituted aliphatic hydrocarbongroup having 2 to 20 carbon atoms,

(5) A degradable polyurethane resin according to the above item (1)wherein saccharides are a single compound or mixture selected frommonosaccharide, molasses, cellulose or cellulose derivative.

(6) A degradable polyurethane resin according to the above item (1)wherein the aliphatic polyhydric alcohol having three or morefunctionality is a single compound or mixture selected from thecompounds represented by the formula (5);

R⁴(OH)_(n)  (5)

wherein R⁴ is a hydrocarbon group having 1 to 20 carbon atoms and n isan integer of 3 to 6.

(7) A degradable polyurethane resin according to the above item (1)wherein the polyol has acidity of 10⁻⁴ mol/g or less.

(8) A degradable polyurethane resin according to the above item (1)wherein the modified compound of2,5-/2,6-diisocyanatomethylbicyclo[2.2.1]heptane is a single compound ora mixture selected from the group consisting of isocyanurate derivativeof 2,5 and/or 2,6-diisocyanatomethylbicyclo[2.2.1]heptane represented bythe formula (6);

or a blocked compound thereof, uretidione derivative of 2,5- and/or2,6-diisocyanatomethylbicyclo[2.2.1]heptane represented by theformula(7);

or a blocked compound thereof, biuret derivative of 2,5- and/or2,6-diisocyanatomethylbicyclo[2.2.1]heptane representd by theformula(8);

or a blocked compound thereof, trimethylolpropane adduct of 2,5- and/or2,6-diisocyanatomethylbicyclo[2.2.1]heptane represented by the formula(9);

or a blocked compound thereof, and polycarbodiimide derivative of 2,5-and/or 2,6-diisocyanatomethylbicyclo[2.2.1]heptane represented by the,formula (10);

wherein Z is an integer of 1 or more.

(9) A degradable polyurethane resin according to the above item (1)wherein 2,5-/2,6-diisocyanatomethylbicyclo[2.2.1]heptane and/or amodified compound thereof are used in an amount of 0.001 to 40% byweight for polyol.

(10) A hydrolyzable polyurethane resin according to one of the aboveitems (1) to (9).

(11) A biodegradable polyurethane resin according to one of the aboveitems (1) to (9).

(12) A raw material composition of degradable polyurethane resincharacterized by comprising the polyol in the above item (1) and2,5-/2,6-diisocyanatomethylbicyclo[2.2.1]heptane and/or a modifiedcompound thereof.

(13) A polymer film characterized by forming the degradable polyurethaneresin of the above item (1).

(14) A polymer sheet characterized by forming the degradablepolyurethane resin of the above item (1).

(15) A base material for disk case characterized by molding thedegradable polyurethane resin of the above item (1).

(16) A polymer staple characterized by forming the degradablepolyurethane resin of the above item (1).

(17) A card base characterized by molding the degradable polyurethaneresin of the above item (1).

BEST MODE OF CARRYING OUT THE INVENTION

Hereinafter, the present invention is illustrated in detail.

The present invention is a degradable polyurethane resin obtained byreacting 2,5/2,6-diisocyanatomethylbicyclo[2.2.1]heptane and/or amodified compound thereof with a single compound, mixture orcopolycondensate of polyol which is selected from the group consistingof (A) polyhydroxycarboxylate polyol, (B) aliphatic polyester polyol and(C) saccharide, or (D) straight or branched polyol which is obtained bycondensation of (A) and/or (B) with tri or more functional aliphaticpolyhydric alcohol.

The degradable polyurethane resin of the invention (hereinafter referredto simply as polyurethane resin of the invention) has hydrolyzablilityand biodegradability. That is, the polyurethane resin of the inventionhas property for causing hydrolysis in the presence of acid or alkaliand also hydrolyzes by hydrolase of microorganisms under naturalenvironment, that is, so called biodegradability.

Consequently, after using for the desired object, for example, moldedarticles, the polyurethane resin of the invention can be destructed byhydrolysis or subjected to recycled use and does not impair globalenvironment, even though abandoned in the natural environment. The resinalso has good strength, elongation and elasticity in addition to suchdegradability.

The polyol of the invention is a single compound, mixture orcopolycondensate which is selected from the group consisting of (A)polyhydroxycarboxylate polyol, (B) aliphatic polyester polyol and (C)saccharides, or (D) straight or branched polyol resulting fromcondensation of (A) and/or (B) with aliphatic polyhydric alcohol havingfunctionality of three or more.

In these polyols, (A) polyhydroxycarboxylate polyol is referred to as anoligomer and/or polymer obtained from aliphatic hydroxycarboxylic acidand the terminal carboxyl group is modified to a hydroxyl group.

That is, (A) polyhydroxycarboxylate polyol of the invention is oligomerand/or polymer of aliphatic hydroxycarboxylic acid represented by theformula (2);

wherein R¹ is an alkylene group having 1 to 4 carbon atoms in thestraight chain portion and having 1 to 6 total carbon atoms whichinclude branched alkyl groups, and m is an integer 1 or more, and theterminal carboxyl group is modified to a hydroxyl group, and includes,for example, a compound represented by the formula(2-1) or formula(2-2);

wherein R¹ is an alkylene group having 1 to 4 carbon atoms in thestraight chain portion and having 1 to 6 total carbon atoms whichinclude branched alkyl groups, R² is an unsubstituted or substitutedaliphatic alkyl group having 2 to 20 carbon atoms, and a and b areintegers of 1 or more.

In the formula (2), (2-1) and (2-2), R¹ is more specifically an alkylenehaving one carbon atom: alkylene having one carbon atom in the straightchain portion and substituted by methyl, ethyl or propyl; alkylenehaving two carbon atoms in the straight chain portion and substituted bymethyl or ethyl; or alkylene having three carbon atoms in the straightchain portion and substituted by methyl. When m is an integer of 2 ormore, R¹ can consist of the same or different structural units.

Specific examples of aliphatic hydroxy carboxylic acid used forpreparing the oligomer or polymer represented by the formula (2)include, for example, glycolic, lactic, 2-hydroxybutyric,3-hydroxybutyric, 4-hydroxybutyric, 2-hydroxyvaleric, 3-hydroxyvaleric,4-hydroxyvaleric, 2-hydroxyhexanic, 2-hydroxyheptanic, 2-hydroxyoctanic,2-hydroxy-2-methyl-butyric, 2-hydroxy-2-ethylbutyric,2-hydroxy2-methylvaleric, 2-hydroxy-2-ethylvaleric,2-hydroxy-2-butylvaleric, 2-hydroxy-2-methylhexanic,2-hydroxy-2-ethylhexanic, 2-hydroxy-2-propylhexanic,2-hydroxy-2-butylhexanic, 2-hydroxy-2-pentylhexanic,2-hydroxy-2-methylheptanic, 2-hydroxy-2-ethylheptanic,2-hydroxy-2-propylheptanic, 2-hydroxy-2-butylheptanic,2-hydroxy-2-pentylheptanic, 2-hydroxy-2-hexylheptanic,2-hydroxy-2-met.hyloctanic, 2-hydroxy-2-ethyloctanic,2-hydroxy-2-propyloctanic, 2-hydroxy-2-butyloctanic,2-hydroxy-2-pentyloctanic, 2-hydroxy-2-hexyloctanic,2-hydroxy-2-heptyloctanic, 5-hydroxy-5-propyloctanic, 6-hydroxycaproic,6-hydroxyheptanic, 6-hydroxyoctanic, 6-hydroxy-6-methylheptanic,6-hydroxy-6-methyloctanic, 6-hydroxy-6-ethyloctanic, 7-hydroxyheptanic,7-hydroxyoctanic, 7-hydroxy-7-methyloctanic and 8-hydroxyoctanic acid.

In these acids, glycolic, lactic, 2-hydroxbutyric, 3-hydroxybutyric,3-hydroxyvaleric and 4-hydroxyvaleric acid are preferred in view ofproviding biodegradable polyurethane resin having high strength. Lacticacid is most preferred because resulting biodegradable resin hasparticularly high strength, is transparent and further has fungusresistance.

The hydroxycarboxylic acid which can be used in the invention is notlimited to the above exemplified compounds and can be used singly or asa mixture for preparing the polymer.

These hydroxycarboxylic acids can also be derived from lactones such asγ-butyrolactone which is formed by intermoleculardehydration-cyclization or from dimers such as glycolide and lactide. Noparticular restriction is imposed upon the ratio of optical isomers.

(B) Aliphatic polyester polyol in the invention can be obtained bypolycondensation of aliphatic polyhydric alcohol with polybasic acid.Aliphatic polyhydric alcohol used for the raw material is, for example,glycols represented by the formula (3):

HO—R²—OH  (3)

wherein R² is an unsubstituted or substituted hydrocarbon group having 2to 20 carbon atoms. Specific glycols include, for example,ethyleneglycol, diethyleneglycol, triethyleneglycol, propyleneglycol,dipropyleneglycol, 1,3-butanediol, 1,4-butanediol,3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol,neopentylglycol, polytetramethyleneglycol and 1,4-cyclohexanedimethanol.In these glycols, ethyleneglycol, 1,4-butanediol and 1,4-cyclohexanedimethanol are preferred in view of availability and ease handling.However, no particular limitation is imposed upon the raw materialsother than these exemplified compounds so long as these materials canform aliphatic polyester. Other polyhydric alcohols can also be used.

Aliphatic polybasic acid used for the raw material is represented by theformula (4);

HOOC—R³—COOH  (4)

wherein R³ is an unsubstituted or substituted aliphatic hydrocarbongroup having 2 to 20 carbon atoms. Representative aliphatic polybasicacids include, for example, oxalic, succinic, malonic, glutaric, adipic,pimelic, suberic, azelaic, sebacic, undecanedioic, dodecanedioic, maleicand fumaric acid. These acids can be used singly or as a mixture.

Anhydride or ester of these acids can also be used. No particularrestriction is imposed upon the raw materials of acid component otherthan these exemplified components so long as these component materialscan form aliphatic polyester.

(C) Saccharides of the invention are monosaccharide, disaccharide,oligosaccharide, polysaccharide and/or derivative and modified compoundsthereof. Specific compounds of monosaccharide include, for example,erythrose, threose, ribose, arabinose, xylose, lyxose, allose, altrose,glucose, mannose, gulose, idose, galactose, talose, fructose,glucopyranose, glucofuranose, galactfuranose, arabinopyranose,fructopyranose, 2-deoxyribose, xylulose, ribulose, sedoheptulose,rhamnose, fucose, glucosamine and galactosamine.

Any ratio can be permitted on the optical isomer content. Disaccharideand polysaccharide consisting of the same or different monosaccharide,enolated saccharide, oxidized saccharide, reduced saccharide, glucosideand other modified saccharides, or mixtures of these materials andmolasses can also be used. Saccharides which can be used in theinvention of course include cellulose which is obtained by forming along chain of saccharides, that is, cellulose nitrate, celluloseacetate, ethylcellulose, celluloid viscose rayon, regenerated cellulose,cellophane, cupra, cupraammonium rayon, cuprophane, bemberg,hemicellulose, starch, gum arabic, guano gum, loucastbean gum, aceciagum, chitin, chitose and modified material thereof. No particularrestriction is imposed so long as the saccharides can be used as polyol.

The above (A) to (C) polyols can also be used for the invention afteradjusting the species and amount of functional groups.

That is, the functional groups are modified by reacting with otherhydroxyl compound, carboxylic acid or amino compound and thus modifiedpolyol can be used for the invention.

For example, a terminal hydroxyl or carboxyl group of aliphaticpolyhydroxycarboxylic acid or aliphatic polyester can be converted tosubstantially hydroxyl group alone by previously reacting withpolyhydric alcohol, polybasic acid or polyamine, or can also be reacted,when necessary, with a compound having a functional group other than ahydroxyl group. Further, when saccharides are used, a new polyol can beprepared by mixing or reacting saccharides with other polyols. Forexample, molasses polyol can be prepared by mixing or reacting molasseswith polyols.

When polyol is (A) aliphatic polycarboxylate polyol in particular,terminal groups of hydroxycarboxylic acid or polyhydroxycarboxylic acidare desired to substantially convert to hydroxyl groups by reacting withone or more species selected from the group consisting of polyhydricalcohol, (B) aliphatic polyesterpolyol and saccharides.

The oligomer and/or polymer of (B) aliphatic polyester polyol obtainedby polycondensation of aliphatic polyhydric alcohol and aliphaticpolybasic acid is desired to substantially terminate the polymer chainwith hydroxyl groups by controlling the mole ratio of aliphaticpolyhydric alcohol to aliphatic polybasic acid.

The polyol which is substantially terminated by hydroxyl groups isreferred to polyol having satisfactory hydroxyl groups to formpolyurethane resin by reacting with NBDI. The polyol has an acid valueof preferably 10⁻⁴ mol/g or less, more preferably 6×10⁻⁵ mol/g or lessby neutralization titration with sodium methylate. As to the hydroxylvalue, an average number of hydroxyl group per mole of polyol isgenerally 1.5 or more, preferably 1.8 or more, more preferably 1.9 ormore, most preferably 2.0 or more.

When controlling the hydroxyl number at the polymer chain end polyolhaving a straight molecular structure can be converted to a branchedmolecular structure by reaction with aliphatic three or more functional,aliphatic polyhydric alcohol represented by the formula (5):

R⁴(OH)_(n)  (5)

wherein R⁴ is a hydrocarbon group having 1 to 20 carbon atoms and n isan integer of 3 to 6. The aliphatic polyhydric alcohol can be usedsingly or as a mixture.

Specifically, polyols having a branched structure can be obtained bycondensation with glycerol, pentaerythritol, trimethylolpropane,trimethylolethane, trimethylolheptane, 1,2,4-butanetriol,1,2,6-hexanetriol or saccharides, on or after preparing aliphaticpolyester polyol by polycondensation of aliphatic polyhydroxycarboxylatepolyol or aliphatic polyhydric alcohol with polybasic acid.

The molecular weight of polyol used in the invention can be controlledby converting high molecular weight to low molecular weight or viceversa. For example, polyhydroxycarboxylic acids or other aliphaticpolyesters can be further polymerized to increase molecular weight orhigh molecular weight cellulose can be decomposed to use as a lowmolecular weight oligomer.

The molecular weight of polyol used can be changed corresponding tovarious uses and thus is not limited in particular. The number averagemolecular weight is usually in the range of 200 to 100,000. As topolysaccharides, higher molecular weight is often used.

In order to obtain biodegradable polyurethane resin having still higherstrength, the weight average molecular weight of aliphaticpolyhydroxycarboxylate polyol and aliphatic polyesterpolyol is in therange of preferably 500 to 100,000, more preferably 1,000 to 50,000,most preferably 5,000 to 40,000. When the weight average molecularweight exceeds 100,000, the amount of NBDI required for the reactionbecomes very small and thus effect of NBDI is reduced.

The isocyanate compound of the invention is NBDI represented by theformula (1):

wherein the two isocyanatomethyl groups are located on 2,5-positions or2,6-positions or a mixture thereof, and/or a modified compound thereof.The modified compound which is preferred in view of preparation andavailability with ease includes, for example, isocyanurate compound ofNBDI represented by the formula (6):

or a blocked compound thereof, uretidione compound of NBDI representedby the formula(7):

or a blocked compound thereof, biuret compound of NBDI represented bythe formula(8):

or a blocked compound thereof, trimethylolpropane adduct compound ofNBDI represented by the formula (9):

or a blocked compound thereof, and polycarbodiimide compound of NBDIrepresented by the formula (10):

wherein Z is an integer of 1 or more, or a blocked compound thereof.

The isocyanate compounds which can be used in the invention are notlimited to these compounds and can be used singly or as a mixture.

In the invention, the desired polyurethane resin can be obtained byreaction of the above polyol with NBDI. However, no particularrestriction is imposed upon the reaction process.

The reaction can be carried out in the presence or absence of solventand catalyst. There reaction temperature can be adequately andarbitrarily controlled depending upon the properties of polyol for useand resulting polyurethane resin.

The amount of NBDI in the reaction can be altered depending upon themolecular weight of polyol, numbers of functional groups on the terminalof polyol and desired properties, and is usually 0.001 to 40% by weight,preferably 0.01 to 25% by weight, more preferably 0.01 to 10% by weight,most preferably 0.01 to 5% by weight for the total amount of rawmaterials used in the reaction. When the amount exceeds 40% by weight,characteristics of polyol can not be fully exhibited. On the other hand,the amount less than 0.001% by weight almost eliminates the effect ofreacting with NBDI.

Solvents which can be used in the invention includes, for example,water, benzene, toluene, xylene, mesitylene, chlorobenzene,o-dichlorobenzene, methylene chloride, chloroform, carbon tetrachloride,dichloroethane, trichloroethane, trichloroethylene, tetrachloroethane,tetrachloroethylene, tetrahydrofuran, 1,4-dioxane,N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone,1,3-dimethyl-2-imidazolidinone, dimethylsulfoxide and sulfolane.

When urethane catalyst is used, specific examples of the catalyst aredibutyltin dilaurate, tetramethylbutanediamine,1,4-diaza[2.2.2]bicyclooctane, stannous octoate, 4-methylmorpholine andtriethylamine. The amount of urethane catalyst is similar to the case ofknown urethane reactions.

The reaction temperature depends upon the polyol used and species offormed polyurethane resin. The reaction is usually carried out in themolten state without solvent in the temperature range of 60 to 250° C.In the presence of the solvent, the reaction is usually carried out inthe range from room temperature to the boiling point of the solvent.

In the invention, a prepolymer substantially terminated by isocyanategroups is prepared by reacting polyol with NBDI, and the reaction can befurther carried out to obtain degradable polyurethane resin. Forexample, a substantially isocyanate terminated prepolymer is obtained byreacting NBDI with aliphatic polyesterpolyol of straight polymer chain,and thereafter the prepolymer can be converted to polyurethane foam inthe presence of water or to biodegradable polycarbodiimide in thepresence of carbodiimide catalyst and further to degradable orbiodegradable polyurethane foam.

Thus obtained polyurethane resin of the invention has urethane linkageformed by reaction of the above polyol and NBDI, and the resin structurehas additional linkages, for example, urea, amide, carbodumide,allophanate, biuret, isocyanurate, urethonimine and imide linkage. Thepresence of these linkages can be arbitrarily selected on the basis ofspecies of NBDI and/or modified compound thereof, species of functionalgroup of the above polyol and reaction conditions.

For example, in order to obtain degradable and biodegradablepolyurethane resin having an isocyanurate linkage, isocyanurate of NBDIis used as a raw material, or functional groups on the terminal arepreviously converted to isocyanate groups by reacting polyol with NBDIand the resulting prepolymer is successively reacted in the presence ofisocyanurate catalyst to form degradable and biodegradable polyurethaneresin having an isocyanurate linkage.

The degradable polyurethane resin particularly obtained in the inventionis also an excellent biodegradable resin having high elasticity andflexibility together with stiffness which is absent in the conventionalbiodegradable resin. Specific linkages such as carbodiimide or imide canprovide resistance to heat and chemicals and thus the degradable andbiodegradable resin can develop new uses.

The term “degradability” which is an excellent property of polyurethaneresin in the invention is referred to a phenomenon which hydrolyzes byaqueous acid or alkali solution and becomes soluble in water. Forexample, a powdered resin decomposes into a water soluble state in anaqueous alkali solution having a sufficient alkali content attemperature in the range of room temperature to 100° C. within 72 hours,preferably within 24 hours, more preferably within 5 hours. Sufficientalkali content is usually more than mole numbers of structural units inthe resin.

The term “biodegradability” is referred to a phenomenon which hydrolyzesto water and carbon dioxide by the catalytic action of hydrolase ofmicroorganisms under natural environment.

The reaction velocity of NBDI and/or modified compound thereof is veryhigh as compared with that of isophorone diisocyanate, which reducesoperation load in the production step and thus the polyurethane resinobtained is excellent in industry.

The polyurethane resin of the invention is a biodegradable resin havingelasticity and flexibility together with stiffness, and can be appliedto various uses. The uses are, for example, polymer film, polymer sheet,tube, foam, filament and other articles obtained by common processingmethod, short fiber, long fiber, nonwoven fabric, porous substrate,defecation bag, garbage bag, sand bag, heat insulating case, food tray,wrapping film, chopsticks, spoon, fork, cup, sponge, bottle, waterabsorption sheet, moisture retention sheet, agricultural mulching film,disc-case substrate, polymer staple, card base, blister package, tobaccofilter, paper coating agent, laminate, lacrimatomic antitussive rod,microcapsule for heat-sensitive paper and pressure sensitive paper,microcapsule for medicine, slow release medicine, microcapsule forfertilizer and soil improver, suture, suture clip, injection syringe,disposable cloth, surgical apparatus, complex semipermeable membrane,fracture therapeutic supporter, bone conjugator, grafting apparatus,implant, fishline, fishing net, fishing lure, bone pot, nail polisher,bathing pumice, horticultural implement, antibromic microcapsule orcontainer or package, microcapsule or container or package of fragrantsubstance, shrink film for label, adhesive, hot-melt adhesive, containerfor recovered waste paper, package band, adhesive tape, cushioningmaterial, coin-packing film, masking film for coating and spectacleframe. For these uses, the polyurethane resin of the invention can bewidely applied by utilizing excellent properties such as degradability,biodegradability in particular.

Particularly, the biodegradable resin obtained by the reaction ofaliphatic polyhydroxy carboxylic acid and NBDI has stiffness andtransparency and thus is excellent for the material of packaging polymerfilm, polymer sheet, disc-case substrate and card base. The polyurethaneresin is also suited for fashion textiles and nonwoven fabric due to itselegant feeling as a cloth.

Preparation process of polymer film, polymer sheet, disc-case substrateand card base includes, for example, solution casting and calendaring.When solution casting is carried out, solvents which can be used are,for example, chloroform, methylene chloride, benzene, acetonitrile,acetone, toluene, xylene, N,N-dimethylformamide, dimethyl sulfoxide,1-methyl-2-pyrrolidone, and 1,3-dimethyl-2-imidazolidinone. The solutionobtained is cast on a flat, smooth surface and the solvent is removed.

When melt extrusion process is carried out, a known T-die method orinflation method is applied. No particular limitation is imposed uponthe extrusion temperature because melting temperature differs dependingupon the species of resin prepared. The temperature range is usually 100to 280° C., when the forming temperature is low, stability of formingprocess is difficult to obtain and overloading is liable to occur. Onthe other hand, high forming temperature tends to generate polymerdecomposition and results in molecular weight reduction, strengthlowering and coloration.

Polymer film or polymer sheet of the invention can be stretched orunstretched. In order to improve stiffness, fabrication ability,mechanical strength, hardness, impact strength, dimensional stabilityand flexural strength, the resulting film or sheet is preferablysubjected to monoaxial or biaxial stretching. When monoaxial stretchingis carried out, the film or sheet is usually stretched 1.1 to 5 times tothe longitudinal or transverse direction. When biaxial stretching iscarried out, stretching on the first axis and the second axis can becarried out simultaneously or successively.

The stretching temperature differs depending upon the structure andconstitution of polyurethane resin used, and is preferably in the rangebetween the glass transition temperature Tg of the polyurethane resinand Tg+50° C. When the stretching temperature is higher than this range,strength improvement due to stretching cannot be observed.

The formed product obtained can also be heat-treated after forming attemperature from Tg to lower than melting point. Heat treatment isusually carried out for 1 second to 30 minutes.

When the polyurethane resin of the invention is processed to formarticles, the resin can also be used as a mixture or complex with otherresin. In order to improve properties, light stabilizer, plasticizer,antioxidant, heat stabilizer, filler, coloring inhibitor, pigment andother additives can be used.

Thus, the polyurethane resin of the invention and formed articlesthereof can be obtained. The formed articles have hydrolyzability andthus, after using for the desired object. These articles can behydrolyzed in an aqueous acid or alkali solution, or biodegraded by theaction of microorganisms under natural environment.

The biodegradable resin in the invention is primarily referred to acompostable resin, for example, which has a carbon dioxide decompositiondegree of 60% or more for the period of 3 months in the biodegradabilitytest in accordance with ISO/CD 14855. The resin which has adecomposition degree of less than 60% has poor biodegradability andcauses problems when disposed as wastes or released into the naturalenvironment in the course of composting.

The raw material composition of degradable polyurethane resin in theinvention comprises the above (1) polyol and NBDI and/or a modifiedcompound thereof and can be converted to the polyurethane resin of theinvention by temperature rise or addition of catalyst or other reactioninitiators.

The composition comprises, for 100 parts by weight of the above (1) (A)to (D) polyol, NBDI and/or modified compound thereof in an amount of0.001 to 70 parts by weight, preferably 0.01 to 30 parts by weight, morepreferably 0.01 to 10 parts by weight, and also comprises aliphaticpolyhydric alcohol, preferably biodegradable polyhydric alcohol in anamount of 0 to 1,000 parts by weight, preferably 0 to 300 parts byweight, more preferably 0 to 100 parts by weight. Further, thecomposition can also comprise catalyst, water or other foaming agent,light stabilizer, plasticizer, antioxidant, heat stabilizer, filler,coloring inhibitor, pigment and other additives. Aliphatic polyhydricalcohol can be present or absent in the composition. When the amountexceeds 50 parts by weight or more, in particular, the aliphaticpolyhydric alcohol preferably has biodegradability.

EXAMPLE

The invention will hereinafter be illustrated further in detail by wayof examples and comparative examples. However, these examples do notlimit the scope of the invention.

Hydroxyl Value

Measured in accordance with JIS K-0070 and shown by mol/g unit.

Weight Average Molecular Weight

Measured by GPC in chloroform solution depending upon species andmolecular weight of polymer.

Acid Value and Number Average Molecular Weight

Measured by automatically titrating with a N/100-sodiummethylate/methanol solution in a solution of methylenechloride/methanol=7/3 by volume and calculated numbers of terminalcarboxylic acid.

Synthesis Example 1 Preparation of Polylactic Acid ModifiedPolyesterpolyol (a) to (d)

After nitrogen-purging a 1 liter five necked flask equipped with astirrer, thermometer, condenser and nitrogen inlet tube, 100.0 g (0.0862mol as carboxyl group) of high molecular polylactic acid obtained byself-dehydration condensation and having a weight average molecularweight of 3,000 and number average molecular weight of 1,160, and 300 gof methylene chloride were charged, successively 17.48 g (0.103 mol) of2-chloro-1,3-dimethylimidezolidinium chloride (hereinafter referred tosimply as DMC), 9.01 g(0.10 mol) of 1,4-butanediol and 24.12 g (0.259mol) of β-picoline were added, and reacted by stirring at 30 to 40° C.for 3 hours. After finishing the reaction, the reaction mixture wassuccessively washed with a 30% aqueous hydrogen chloride solution andwater. Thereafter methylene chloride was removed by warming underreduced pressure to obtain 105.3 g of polylactic acid modifiedpolyesterdiol. The yield was 100%. Polylactic acid modifiedpolyesterdiol(a) thus obtained had a weight average molecular weight of3,000 by GPC, acid value of 1.17×10⁻⁵ mol/g, and hydroxyl value of1.92×10⁻³ mol/g. The amount of 1,4-butanediol was changed to 0.060 mol,0.030 mol and 0.015 mol and the amounts of DMC and β-picoline werecorrespondingly varied to obtain polylactic acid modified polyesterdiolshaving a weight average molecular weight of 5,000 (polyester-polyol(b)),10,000(polyesterpolyol (c)), and 20,000(polyesterpolyol(d)),respectively. Polylactic acid modified polyesterdiols thus obtained hadan acid value of 1.42×10⁻⁵, 1.33×10⁻⁵ and 1.14×10⁻⁵ mol/g, respectivelyand hydroxyl value of 1.21×10⁻³, 6.02×10⁻⁴ and 2.99×10⁻⁴ mol/g,respectively.

Synthesis Example 2 Preparation of Polylactic Acid ModifiedPolyesterpolyol (e) to (h)

After nitrogen-purging a 1 liter five necked flask equipped with astirrer, thermometer, condenser and nitrogen inlet tube, 100.0 g (0.0862mol as carboxyl group) of high molecular polylactic acid obtained byself-dehydration condensation and having a weight average molecularweight of 3,000 and number average molecular weight of 1,160, and 300 gof methylene chloride were charged, successively 17.48 g (0.103 mol) ofDMC, 5.59 g of ethylene glycol and 0.91 g of pentaerythritol (the molratio of ethylene glycol to pentaerythritol was 9:0.67) and 24.12 g(0.259 mol) of β-picoline were added, and reacted by stirring at 30 to40° C. for 3 hours. After finishing the reaction, the reaction mixturewas successively washed with a 30% aqueous hydrogen chloride solutionand water. Thereafter methylene chloride was removed by warming underreduced pressure to obtain 104.9 g of polylactic acid modifiedpolyesterdiol. The yield was 100%. Polylactic acid modifiedpolyesterpolyol(e) thus obtained had a weight average molecular weightof 3,000 by GPC, acid value of 1.18×10⁻⁵ mol/g, and hydroxyl value of1.88×10⁻³ mol/g. Polylactic acid modified polyesterdiol having an weightaverage molecular weight of 5,000(f), 10,000(g) and 20,000(h),respectively were prepared on the basis of the same mol ratio exceptthat total mol ratio of ethylene glycol and pentaerythritol was variedto 0.0580 mol, 0.0290 mol and 0.0145 mol, respectively.

Polylactic acid modified polyesterdiol thus obtained had a hydroxylvalue of 1.21×10⁻³, 6.11×10⁻⁴ and 3.06×10⁻⁴ mol/g, respectively.

Synthesis Example 3 Preparation of Succinic Acid-base Polyester (i)

To a 3 liter separable flask equipped with a stirrer, fractionatingcondenser, thermometer and nitrogen inlet tube, 750 g of 1,4-butanediol,885 g of succinic acid and 1.6 g of tetraisopropyl titanate werecharged, esterified in a nitrogen stream at 195 to 200° C., and finallya deglycolation reaction was carried out at 210 to 215° C. for 6 hoursunder reduced pressure of 0.6 torr. As a result, succinic acid-basepolyester (i) having an weight average molecular weight of 17,000 wasobtained. Polyester (i) was cooled to room temperature and solidified towhite wax having a melting point of 110 to 115° C.

Preparation of Adipic Acid-base Polyester(j)

To the same flask as used for the above succinic acid-base polyester,750 g of 1,4-butanediol, 1,095 g of adipic acid and 1.8 g oftetraisopropyl titanate were charged and esterified at 190 to 200° C.for 6 hours under nitrogen atmosphere and thereafter deglycolationreaction was carried out at 205 to 210° C. for 7 hours finally underreduced pressure of 0.5 torr. As a result, adipic acid-base polyester(j) having a weight average molecular weight of 15,000 was obtained.Polyester (j) was cooled to room temperature and solidified to faintyellow wax having melting point of 58° C.

Synthesis Example 4 Preparation of Polylactic Acid ModifiedPolyesterdiol (k) to (m)

After dissolving 100.0 g (0.0862 mol as carboxyl group) of polylacticacid oligomer which had a weight average molecular weight of 3,000 andwas used in Synthesis Example 1 into 300 g of methylene chloride at 40°C., 0.90 g (0.01 mol) of 1,4-butanediol 17.48 g (0.103 mol) of DMC and24.12 g (0.259 mol) of β-picoline were successively added and reacted at40° C. for 3 hours. After finishing the reaction, reaction mixture wasdiluted to 10%, successively washed with a 30% aqueous hydrogen chloridesolution and water, and concentrated in an evaporator to removemethylene chloride. Polyesterdiol (k) thus obtained had a weight averagemolecular weight of 30,000 and a molecular weight distribution degree of3.0. By repeating the same procedures as above except the amount of1,4-butanediol was varied to 0.43 g and 0.347 g, respectively,polylactic acid modified polyesterdiol having a weight average molecularweight of 65,000 (1) and 78,000 (m), respectively, was obtained.

Examples 1 to 4

Into a 200 ml flask, 100 g of polylactic acid modified polyesterdiol (a)which was obtained in Synthesis Example 1 and had a weight averagemolecular weight of 3,000, was charged, heated and melted. Astoichiometric amount, that is, 19.8 g (0.096 mol) of NBDI was slowlyadded over 30 minutes and maintained as such for an hour to obtaindegradable polyurethane resin (hereinafter referred to as polyurethaneresin) having a melting point of 170° C.

In Examples 2 to 4 and Comparative Example 1 below, polyurethane resinswere prepared by using polyesterdiol had a weight average molecularweight of 5,000 (polyol (b) in Example 2), 10,000 (polyol (c) in Example3), and 20,000 (polyol (d) in Example 4), respectively. Any polyurethaneresin prepared in Examples 1 to 4 had a weight average molecular weightof 100,000 or more. The amount of NBDI was 0.5 mol times of the numberof hydroxyl group in polyol. Polyurethane resin obtained was formed intoa film having a thickness of 100 μm and properties of the film weremeasured. Properties of the resin are shown in Table 1.

Example 5

Into a flask, 50 g of polylactic acid modified polyesterdiol (a) whichwas obtained in the same procedure as Synthesis Example 1 and had aweight average molecular weight of 3,000, and an equivalent amount ofNBDI isocyanurate compound were charged, heated under nitrogen stream,and melted with stirring for an hour. The reaction mass was dischargedon a stainless steel plate under nitrogen stream to obtain polyurethaneresin. Properties of the polyurethane resin are shown in Table 1.

Example 6

The same procedures as Example 5 were carried out except NBDIurethondion compound was used as a NBDI modified compound. Polyurethaneresin was obtained. Properties of the polyurethane resin obtained areshown in Table 1.

Example 7

The same procedures as Example 5 were carried out except NBDI biuretcompound was used as a NBDI modified compound. Properties ofpolyurethane resin obtained are shown in Table 1.

Example 8

The procedures of Example 5 were repeated except NBDI trimethylolpropaneadduct compound was used as a NBDI modified compound. Properties ofpolyurethane resin obtained are shown in Table 1.

Example 9

The procedures of Example 5 were repeated by using NBDI carbodiimidecompound having average repeating units of 5. Properties of polyurethaneresin obtained are shown in Table 1.

A test specimen obtained by fusion molding of the polyurethane resin at240° C. had heat distortion temperature of 171° C., which was goodresistance to heat as biodegradable resin.

Example 10

After melting 100 g of polylactic acid modified polyesterpolyol(e) whichwas obtained in Synthesis Example 2 and had an weight average molecularweight of 3,000 by heating to 200° C. NBDI was dropwise added over 30minutes. NBDI was used in a stoichiometric amount to the hydroxyl groupof polylactic acid modified polyesterpolyol. After mixing for an hour,the reaction mass was discharged on a stainless steel plate undernitrogen stream to obtain polyurethane resin. A press-film was preparedand properties are shown in Table 1.

Example 11

Procedures of Example 10 were repeated by using polylactic acid modifiedpolyesterpolyol which was obtained in Synthesis Example 2 and had aweight average molecular weight of 5,000. Properties of polyurethaneresin thus obtained are shown in Table 1.

Example 12

Procedures of Example 10 were repeated by using polylactic acid modifiedpolyesterpolyol which was obtained in Synthesis Example 2 and had aweight average molecular weight of 10,000. Properties of polyurethaneresin obtained are shown in Table 1.

Example 13

Procedures of Example 10 were repeated by using polylactic acid modifiedpolyesterpolyol which was obtained in Synthesis Example 2 and had aweight average molecular weight of 20,000. Properties of polyurethaneresin obtained are shown in Table 1.

Comparative Example 1

After dissolving 100 g of polylactic acid having a number averagemolecular weight of 1,500 into 300 g of benzene, 13.52 g (0.08 mol) ofDMC and 17.88 g (0.192 mol) of β-picoline were charged, stirred forseveral minutes and allowed to stand for 2 hours.

The reaction mixture was diluted to 10% concentration, washedsuccessively with a 30% aqueous hydrochloric acid solution and water,poured into a large amount of isopropyl alcohol, filtered and dried toobtain polylactic acid powder. The polylactic acid powder had a weightaverage molecular weight of 193,000. The molecular weight wassufficiently high for confirming properties. Specimens were preparedfrom the polylactic acid powder and properties were measured and shownin Table 1. According to the results, any polylactic acid-basepolyurethane resin prepared in Examples 1 to 13 have improved mechanicalproperties as compared with polylactic acid prepared in ComparativeExample 1. Biodegradability is almost equal. The polymer sheet preparedfrom polylactic acid of Comparative Example 1 had no flexibility and wasbroken by 180 degree bending.

Comparative Example 2

Polylactic acid modified polyesterdiol obtained in Synthesis Example Iand had a weight average molecular weight of 10,000 was used. Aftercharging and heat-melting 100 g of the polyesterdiol, 2.44 g ofhexamethylene-diisocyanate was added and stirred for an hour. Viscosityincreased rapidly, but gelation did not occur. After finishing thereaction, the reaction mass was discharged into a stainless steel plateto obtain polyurethane resin. Properties of polyurethane resin thusobtained was measured and shown in Table 1. According to the results,polyurethane resin of Example 4 has more excellent mechanical propertiesand almost equal biodegradability as compared with polyurethane resin ofComparative Example 2.

Comparative Example 3

Polylactic acid modified polyesterdiol(c) obtained in Synthesis Example1 and had a weight average molecular weight of 10,000 was used. To aflask, 100 g of the polyesterdiol(c) was charged, melted by heating and3.98 g of isophorone diisocyanate was added and stirred for 1 hour.Viscosity increase was slow and similar molecular weight as Example 4could not be obtained even after stirring for 6 hours. That is, reactionvelocity was very slow. After finishing the reaction, the reaction masswas discharged to a stainless steel plate to obtain polyurethane resin.Test specimen was prepared by forming polyurethane resin thus obtained.Results of testing properties are shown in Table 1. According to theresults, polyurethane resin of Example 4 has more excellent mechanicalproperties and almost equal biodegradability as compared withpolyurethane resin obtained in Comparative Example 3. Polymer sheetprepared from polyurethane resin obtained in Comparative Example 3 hadpoor flexibility and was broken by 180 degree bending.

Biodegradability

Biodegradability of polyurethane resin prepared in Examples 1 to 13 andComparative Examples 1 to 3 was measured in accordance with ISO/CD14855. Results are shown in Table 1.

Tensile Test

Tensile test of biodegradable resin obtained in Examples 1 to 13 andComparative Examples 1 to 3 was carried out in accordance with JISK-7113. Results are shown in Table 1.

TABLE 1 Biodegradability Mechanical Property Degradation Tensile Elasticafter 3 strength Elongation modulas month MPa % MPa Example 1 84 68 444110 Example 2 81 66 32 4800 Example 3 83 68 22 4230 Example 4 82 70 214390 Example 5 80 77 18 6450 Example 6 83 66 17 4690 Example 7 84 67 614120 Example 8 82 68 33 4270 Example 9 79 72 11 4290 Example 10 83 69 284430 Example 11 81 70 27 4240 Example 12 85 73 30 4480 Example 13 84 7332 4650 Comparative 85 65  7 3380 Example 1 Comparative 83 39 35 3480Example 2 Comparative 82 48  5 2130 Example 3

Example 14

To a 1 liter separable flask equipped with a stirrer, fractionationcondenser, thermometer and nitrogen inlet tube, 400 g of polyester (i)obtained in Synthesis Example 3 and 100 g of polyester (j) were charged,uniformly heat-melted and evacuated to 1 torr for 10 minutes. Thereafter9.09 g of NBDI was added under ambient pressure at 200° C. in nitrogenstream. Viscosity increased rapidly, but gelation did not occur.Stirring was continued for 30 minutes and the reaction mass wasdischarged on a stainless steal plate. The polyurethane resin obtainedwas hot-pressed to form a press film having thickness of 100 μm. Thefilm was tough and could not be broken by human force.

A transparent film obtained by stretching 3 times to both directions hadtensile strength of 75 MPa.

Example 15

To a 1 liter flask equipped with a stirrer, fractionation condenser,nitrogen inlet tube and thermometer, 300 g (3.33 mol) of 1,4-butanedioland 354 g (3.00 mol) of succinic acid were charged and esterified at 200to 205° C. for 5 hours in a nitrogen stream. Successively, the condenserwas changed to a straight run type, 0.06 g of tetraisopropyl titanatewas added, and deglycolation reaction was carried out at 220° C. underreduced pressure of 0.05 torr for 10 hours. The reaction mass wasdischarged on a stainless steel plate. Polyesterdiol thus obtained was acrystalline product and solidified to white, opaque hard wax. The waxhad a weight average molecular weight of 38,000, acid value of 1.02×10⁻⁵mol/g, and hydroxyl value of 5.88×10⁻⁵ mol/g. To a 300 ml flask equippedwith a stirrer, condenser, nitrogen inlet tube and thermometer, 100 g(5.88×10⁻³ mol as hydroxyl group) of aliphatic polyesterdiol thusobtained was charged, melted at 180° C. and 0.77 g of NBDI was added.Viscosity increased rapidly, but gelation did not occur. Thereafter thereaction was continued for an hour and finished. The obtainedpolyurethane resin was hot-pressed into a film and properties weremeasured. The film had good mechanical properties. Tensile strength atbreak was 68 MPa and elongation at break was 490%.

Example 16

To a 100 ml four necked flask, 14.6 g (0.10 mol) of adipic acid, 9.2 gof 1,4-butanediol, 0.3 g of DL-maleic acid, 0.05 g of methanesulfonicacid and 40 ml of toluene were charged, and a dehydration condensationreaction was carried out at 100 to 110° C. for 7 hours. The reactionproduct had a number average molecular weight of 16,000 and a weightaverage molecular weight of 37,000 by GPC. Hydroxyl value was 1.41×10⁻⁴mol/g. Thereafter, 0.32 g of NBDI was added and reacted at 100° C. for 4hours. At this stage, the reaction mass had a weight average molecularweight 161,000. After finishing the reaction, toluene andmethanesulfonic acid were removed to obtain modified polybutyleneadipate.

Example 17

To a flask, 200 g of xylene and 50 g of polylactic acid modifiedpolyesterdiol(c) which was obtained in Synthesis Example 1 and had aweight average molecular weight of 10,000 were charged and dissolved at100° C. Thereafter, 1.85 g (8.95×10⁻³ mol) of NBDI and 10 mg of1,4-diaza[2.2.2]bicyclooctane were added and reacted for 2 hours.Successively, 10 mg of 3-methyl-1-phenyl-3-phosphoren oxide which is acarbodiimide catalyst was added and reacted at 120° C. for 20 hours.After finishing the reaction, the reaction mixture was cooled, filtered,washed with 500 ml of methyl-tert-butyl ether, and dried under reducedpressure at 80° C. for 12 hours to obtain degradable polyurethanecarbodiimide resin. The resin was hot-pressed at 240° C. to form a sheethaving a thickness of 3 mm. The sheet had a Vicat softening point of174° C. in accordance with JIS K-7206.

Example 18

To a flask, 40 g of cellulose acetate having a weight average molecularweight of 110,000, 60 g of polylactic acid modified polyesterpolyol(a)which was obtained in Synthesis Example 1 and had a molecular weight of5,000, and 300 g of xylene were charged and dissolved at 120° C.Thereafter, 1 g of 1% xylene solution of 1,4-diaza[2.2.2]bicyclooctanewas added, and successively 11.8 g(0.057 mol) of NBDI was charged.Reaction was carried out for 1 hour. After finishing the reaction, thereaction mixture was cooled, filtered, washed with 800 g isopropylalcohol and dried at 80° C. under reduced pressure to obtainpolyurethane resin powder.

The press film prepared from the resin had a tensile strength at breakof 69 MPa, elongation of 260% and tensile elastic modulus of 3,920 MPa.

Example 19

After heat-melting 100 g of polylactic acid modified polyesterdiol(k)which was obtained in Synthesis Example 4 and had a weight averagemolecular weight of 30,000, a stoichiometric amount of NBDI was addedand maintained for an hour to obtain polyurethane resin. The polymerthus obtained was kneaded in an extruder and delivered through a T-diein the form of an unstretched film having a thickness of 800 μm.Properties of the film are shown in Table 2.

Example 20

The procedures of Example 19 were repeated except polylactic acidmodified polyesterdiol (1) having a weight average molecular weight of65,000 in Synthesis Example 4 was used. Properties of a film obtainedare shown in Table 2.

Example 21

The same procedures as Example 19 were carried out by using polylacticacid modified polyesterdiol(m) having a weight average molecular.weightof 78,006 in Synthesis Example 4. Properties of the film thus obtainedare shown in Table 2.

Example 22

The procedures of Example 19 were repeated except polylactic acidmodified polyesterdiol (l) having a weight average molecular weight of65,000 in Synthesis Example 4 and polybutylene succinate having a weightaverage molecular weight of 50,000 were used in a proportion of 90:10.Properties of the film obtained are shown in Table 2.

Example 23

The procedures of Example 19 were repeated except polylactic acidmodified polyesterdiol having a weight average molecular weight of78,000 in Synthesis Example 4 and polybutylene succinate having a weightaverage molecular weight of 50,000 were used in a proportion of 80:20.Properties of the film are shown in Table 2.

TABLE 2 Proportion Strength of Example Mw of X (X:Y) break MPa Example19 10,000 100:0 64 Example 20 65,000 100:0 69 Example 21 78,000 100:0 73Example 22 65,000  90:10 77 Example 23 78,000  80:20 82 Note; MW: weightaverage molecular weight X: polylactic acid modified polyesterdiol Y:polybutylene succinate

Example 24

Polyurethane resin was prepared by repeating the procedures of Example19 except polylactic acid modified polyesterdiol having a weight averagemolecular weight of 30,000 in Synthesis Example 4 was used. Thepolyurethane resin obtained was melt-kneaded with an extruder to form anunstretched sheet having a thickness of 1.2 mm. The polymer sheet thusobtained did not break even after repeating 100 times of 180 degreebending and also had good flexibility.

Example 25

Procedures of Example 24 were repeated except polylactic acid modifiedpolyesterdiol (l) having a weight average molecular weight of 65,000 inSynthesis Example 4 was used. The polymer sheet obtained did not break,even after repeating 100 times of 180 degree bending and also had goodflexibility.

Example 26

Procedures of Example 24 were repeated except polylactic acid modifiedpolyesterdiol (m) having a weight average molecular weight of 78,000 inSynthesis Example 4 was used. The polymer sheet obtained broke afterrepeating 89 times of 180 degree bending. Flexibility was good.

Example 27

Procedures of Example 24 were repeated except polylactic acid modifiedpolyesterdiol (l) having a weight average molecular weight of 65,000 inSynthesis Example 4 and polybutylene succinate having a weight averagemolecular weight of 50,000 were used in a proportion of 90:10.

Example 28

Procedures of Example 24 were repeated except polylactic acid modifiedpolyesterdiol (m) having a weight average molecular weight of 78,000 inSynthesis Example 4 and polybutylene succinate having a weight averagemolecular weight of 50,000 were used in a proportion of 80:20.

Example 29

Polyurethane resin was prepared by the same procedures as Example 19.The polymer obtained was melt-spun with a nozzle mounted extruder toobtain a filament for use in staple fiber. Properties of the staplefilament obtained are shown in Table 3.

Example 30

Polyurethane resin was prepared by the same procedures as Example 20.The polymer obtained was melt-spun with a nozzle mounted extruder toobtain a filament for use in staple fiber. Properties of the filamentobtained are shown in Table 3.

Example 31

Polyurethane resin was prepared by the same procedures as Example 21.The polymer obtained was melt-spun with a nozzle-mounted.extruder toobtain a filament for use in staple fiber. Properties of the filamentobtained are shown in Table 3.

TABLE 3 Melting Tensile Example Mw of X temperature ° C. elongation %Example 29 10,000 175 30 Example 30 65,000 172 40 Example 31 78,000 17340 Note, MW: weight average molecular weight X: polylactic acid modifiedpolyesterdiol Y: polybutylene succinate

Example 32

A rotor was mounted on a screw tube, and 1 g of the polyurethane resinpowder obtained in Examples 1 to 18 and 20 g of a 10 N aqueoussodium.hydroxide solution were charged and stirred with a magneticstirrer at room temperature to 50° C. Any powder was dissolved intowater within an hour. Any polyurethane resin had good hydrolyzability.

Probability of Application in Industry

The degradable polyurethane resin of the invention is prepared by usingan isocyanate bonding agent;2,5-/2,6-diisocyanatomethylbicyclo[2.2.1]heptane and/or a modifiedcompound thereof.

The resin is a polyurethane-base material having degradability that is,hydrolyzability and biodegradability. After using for a desired object,the resin can be hydrolyzed to recover and reuse the raw material. Thatis, recycled use can be accelerated even in the field of difficultyrecycled matter such as printed paper combined with a general purposeresin. For example, paper or card laminated with the polyurethane resinof the invention can be recovered and recycled without isolating fromother general-purpose paper. When compared with conventionally knownbiodegradable resin, the resin of the invention has new combination ofproperties such as rigidity and elasticity and flexibility in additionor outstandingly high elasticity and elongation notwithstanding highstrength. Further, the polyurethane resin of the invention can provideformed-articles having biodegradability.

Consequently, the polyurethane resin of the invention has become capableof applying to a field where conventional biodegradable resin wasunsatisfactory in view of physical properties although biodegradabilitywas good.

The polyurethane resin of the invention can be obtained without heavyload in production as compared with biodegradable resin prepared byusing conventionally known aliphatic diisocyanate as a bonding agent.Further, diamine which generates after degradation has no mutagenicityand thus a biodegradable resin having safety and high adaptability toenvironment can be provided.

What is claimed is:
 1. A degradable polyurethane resin resulting fromreaction of polyol with 2,5/2,6-diisocyanatomethylbicyclo[2.2.1]heptanerepresented by the formula (1):

wherein the two isocyanatomethyl groups are located on 2,5-positions or2,6-positions or a mixture thereof, and/or a modified compound thereof,wherein the polyol is (A) polyhydroxycarboxylate polyol wherein thepolyhydroxycarboxylate polyol is obtained by modification of theterminal carboxyl group to a hydroxyl group in the aliphaticpolyhydroxycarboxylic acid represented by the formula (2):

wherein R¹ is an alkylene group having 1 to 4 carbon atoms in thestraight chain portion and having 1 to 6 total carbon atoms whichinclude branched alkyl groups, and m is an integer of 1 or more, or amixture or copolycondensate of (A) and one or more compounds selectedfrom (B) aliphatic polyesterpolyol and (C) saccharides.
 2. A degradablepolyurethane resin according to claim 1 wherein R¹ in the formula (2) isan alkylene group having 1 carbon atom, alkylene having 1 carbon atom inthe straight chain portion and substituted by methyl, ethyl or propyl,or having 2 carbon atoms in the straight chain portion and substitutedby methyl or ethyl, or having 3 carbon atoms in the straight chainportion and substituted by methyl, and R¹ in the formula (2) isaliphatic polyhydroxycarboxylate polyol comprising the same or differentstructural units.
 3. A degradable polyurethane resin according to claim1 wherein aliphatic polyesterpolyol is obtained by reacting a singlecompound or mixture selected from aliphatic polyhydric alcoholrepresented by the formula (3): HO—R²—OH  (3) wherein R² is anunsubstituted or substituted aliphatic hydrocarbon group having 2 to 20carbon atoms, with a single compound or mixture selected from aliphaticpolybasic acid represented by the formula(4): HOOC—R³—COOH  (4) whereinR³ is an unsubstituted or substituted aliphatic hydrocarbon group having2 to 20 carbon atoms.
 4. A degradable polyurethane resin according toclaim 1 wherein saccharides are a single compound or mixture selectedfrom monosaccharide, molasses, cellulose or cellulose derivative.
 5. Adegradable polyurethane resin according to claim 1 wherein the polyolhas acidity of 10⁻⁴ mol/g or less.
 6. A degradable polyurethane resinaccording to claim 1 wherein the modified compound of2,5-/2,6-diisocyanatomethylbicyclo[2.2.1]heptane is a single compound ora mixture selected from the group consisting of isocyanurate derivativeof 2,5- and/or 2,6-diisocyanatomethylbicyclo[2.2.1]heptane representedby the formula(6):

or a blocked compound thereof; uretidione derivative of 2,5- and/or2,6-diisocyanatomethylbicyclo[2.2.1]heptane represented by theformula(7):

or a blocked compound thereof; biuret derivative of 2,5- and/or2,6-diisocyanatomethylbicyclo[2.2.1]heptane represented by theformula(8):

or a blocked compound thereof; trimethylolpropane adduct of 2,5- and/or2,6-diisocyanatomethylbicyclo[2.2.1]heptane represented by theformula(9):

or a blocked compound thereof; and polycarbodiimide derivative of 2,5-and/or 2,6-diisocyanatomethylbicyclo[2.2.1]heptane represented by theformula(10):

wherein Z is an integer of 1 or more.
 7. A degradable polyurethane resinaccording to claim 1 wherein2,5-/2,6-diisocyanatomethylbicyclo[2.2.1]heptane and/or a modifiedcompound thereof are used in an amount of 0.001 to 40% by weight fortotal amount of raw materials used in the reaction.
 8. A hydrolyzablepolyurethane resin according to claim
 1. 9. A biodegradable polyurethaneresin according to claim
 1. 10. A raw material composition of degradablepolyurethane resin characterized by comprising the polyol of claim 1 and2,5/2,6-diisocyanatomethylbicyclo[2.2.1]heptane and/or a modifiedcompound thereof.
 11. A polymer film comprising the degradablepolyurethane resin of claim
 1. 12. A polymer sheet comprising thedegradable polyurethane resin of claim
 1. 13. A base material for diskcase comprising the degradable polyurethane resin of claim
 1. 14. Apolymer staple comprising the degradable polyurethane resin of claim 1.15. A card base comprising the degradable polyurethane resin of claim 1.